Shake once without and once with ice, strain into a large coupe glass, and garnish with freshly grated nutmeg.
Other Madeira styles will work as long as the sweetness level is adjusted for (perhaps a bsp of simple syrup for each level down). Malmsey > Bual > Verdelho > Sercial. I think Rainwater is somewhere in the middle.
In needing more Flip ideas for the Winter, I was inspired by Jacob Grier's PX Flip (PX sherry, Angostura, egg). Since Malmsey Madeira is not as sweet as Pedro Ximenez sherry, I took a page from Misty Kalkofen's Fort Washington Flip and sweetened things with maple syrup. While my drink was an off menu item, it did make a menu in late 2017 at the Livestock Tavern in Honolulu.